The present invention relates to the general field of electrical breaker gear, and more particularly to systems enabling breaking to be actuated in this type of gear.
This type of installation comprises one or more electrical breaker poles such as trippable switch-disconnectors, trippable fused switch-disconnectors, trippable switches, and circuit breakers. The main functions of such poles are the following:                setting up and interrupting electric currents on load, on overload, and on short circuits;        protecting a site and personnel against electrical risks; and        guaranteeing user safety (actuation, lockout, and isolation).        
Electrical breaker gear is fitted with a control system connected to the electrical breaker poles and from which circuit breaking is controlled. The control system constitutes the most important safety element of the installation, since it is the control system that determines the level of performance and the reliability of the electrical breaker gear and also provides the interface between a user and the electrical power portion of the electrically powered device(s).
The control system enables the user to changeover the breaker pole(s) to go from a closed position (power on) referred to as a “closing position” to an open position (power off) referred to as a “breaking position” and vice versa, by means of a control handle. More precisely, the control system comprises an accumulator mechanism formed mainly of an inner carriage connected to the control handle and of an outer carriage connected to a breaker pole control shaft, the inner carriage sliding in the outer carriage. A spring is interposed between the two carriages so as to accumulate mechanical energy during movement of the inner carriage by the control handle and to return the energy to the outer carriage at the end of the stroke of the control handle so as to enable quick and reliable opening or closing of the breaker pole(s).
However, in the event of one or more breaker poles becoming welded in the closing position, the outer carriage of the control system, which is connected to the poles by a control shaft, may remain blocked while the control handle has finished its stroke between the closing position and the breaking position. In this event, the control system is no longer usable since welding of one or more poles makes it impossible to control opening of all of the poles.
When welding of one or more breaker poles cannot be overcome by the force of the trip mechanism spring, that leads to very significant safety problems. If the control handle has been moved to reach its position corresponding to the normal position for opening the breaker poles, the operator may think that the pole(s) has/have indeed been opened when that is not so.
Furthermore, safety standards require that the handle can be locked in the breaking position. However, in the event of one or more breaker poles becoming welded, this safety requirement is ineffective if the control handle can be locked in its breaking position while the breaker pole(s) are still in their closed position.